Pervious Concrete Mix Design for Wearing Course Applications (CTRE)
The typical application of pervious concrete in roads consists of full depth pavement to allow for infiltration of stormwater into underlying aggregate and soil, reducing contaminated runoff. However, this experience has proved that pervious concrete possesses many characteristics which would also be beneficial in a surface or wearing course application. These benefits include significantly reduced traffic noise, reduced splash and spray and hydroplanning, and increased friction and skid resistance. However, concerns still existed regarding the compromised strength, freeze-thaw durability, and constructability issues of the pervious concrete as a material in pavements. In response to this concern, a pervious concrete mix design was developed by the CP Tech Center at Iowa State University. This mix was tested in a 4 inch overlay of an existing concrete pavement test section at MnROAD. The mix was designed to be a slip formable, self-consolidating concrete, reinforced with fibers to reduce surface cracking. The design of this overlay material also sought to achieve the following characteristics:
- Sufficient strength and durable aggregate for long-term freeze-thaw durability,
- Porosity around 20% to 25% to maximize noise reduction and minimize maintenance,
- High workability to reduce labor requirements and support uniform porosity throughout the pavement thickness, and
- The ability to maintain voids when compaction is applied by the paver for uniform surface porosity.
Since construction in 2008, the pervious concrete overlay has been tested frequently for ride, noise and other surface characteristics, along with monitoring its response to vacuuming, traffic, and environmental effects. The results show that pervious concrete can be effectively designed for pavement overlays that provides feasible placement and sufficient ride quality. However, continued maintenance (vacuuming and sweeping) of this test section has proved to be a vital step in sustaining the pavement ride and drainability. The results from this study can be found in the reports and presentations below.